This invention relates to density determination and more particularly, to the in situ density measurement of a layer of material disposed on a base layer.
In certain paving operations, very thin layers of asphaltic concrete are overlayed on an existing roadway or base as a wear course. Construction machinery employed in the application of such overlays, which are often as thin as 0.7 inches, are generally constructed and arranged for providing a generally planar upper surface. This can result in thickness and density variations since the underlying surface is likely to be uneven. It is, therefore, desirable to accurately determine the density of such top layers as they are applied so that adjustments can be made to thereby minimize the formation of surface variations which would otherwise result from heavy traffic compressing the thicker and generally less dense portions of the layer.
Present density radiation devices tend to "read" through the thin top layer providing a density measurement that is a composite of the top layer and underlying base courses. As a result, such density measurements are not satisfactory for determining if the compacted top layer conforms to design specifications. It is, therefore, desirable to provide a method for rapidly and accurately determining the density of the applied layer so that correction in the compacting operation can be made thereby minimizing the possibility that costly reworking of the entire paving operation may be required.